Large weldments benefit from automated, high deposition welding. Some applications designed for large weldments employ large robots or gantry-type positioners for moving the weld equipment into position. Other applications require the use of a travel carriage or tractor for carrying the welding equipment.
The Lincoln Electric Co. of Cleveland, Ohio has successfully sold welding carriages known as the LT-7 and LT-56 carriages for many years. These carriages were based upon a three-wheel design—one wheel in the front for guiding and steering and two wheels in the rear for propulsion. The three-wheel design tracked well because all three wheels were in contact with the surface. The disadvantage to the three-wheel design was that in some joint configurations, the carriage is prone to tipping.
Other manufacturers have utilized a four-wheel design. The four-wheel design is less prone to tipping. However, it is more difficult to create a simple steering mechanism and not all four wheels may always be in contact with the ground. Thus, the four-wheel design, like the three-wheel design, is appropriate in certain applications, but is problematic in others.
Both the three-wheel and four-wheel designs are adaptable to track systems. Track systems are used when the weld joint does not provide a reliable path for guiding the carriage. Instead, one or more wheels or guides on the carriage align with the rail on the track to provide direction.
Because of the low demand for welding travel carriages, welding equipment manufacturers generally offer only the three-wheel or only the four-wheel carriage. Further, the cost to consumers to purchase, maintain and operate both three-wheel and four-wheel carriages has generally required consumers to pick between either a three-wheel design or a four-wheel design.
Further, certain large welding applications often require multiple passes from a single welding device to deposit a sufficient amount of weld material to join two or more large work pieces. Current methods and equipment require these multi-pass welds to be accomplished by running the length of a weld with a welding carriage and then repeating the process multiple times with the same carriage to deposit the needed weld material. This process is inefficient.
Additionally, existing welding carriages fail to provide the needed flexibility that is desired for different welding requirements. Specifically, different weldments often require different welding equipment or a different welding equipment configuration. Thus, there is a need for a welding carriage structure to flexible in its applications so as to allow for the carriage to be used in a plurality of different welding applications with little or no modification to the carriage Current welding carriage manufactures attempt to address this by offering for sale various welding carriage kits or configurations, where each separate kit or configuration is to be used for a particular welding application. This solution is costly and requires the welder to store and maintain a number of different welding kits, in addition to the carriage assembly itself.
Accordingly, there is a need for a welding carriage which can operate in as both a three-wheel carriage and a four-wheel carriage, and one which has a modular construction so as to be able to be easily used in a plurality of configurations.